Q. Explain scombroid poisoning?

Ingestion of improperly handled and stored seafood (yellow-fin tuna, skipjack, bonit and mackerel) causes scombroid poisoning. Maitoxin has been implicated in scombroid poisoning,which releases neurotransmitters and increases the contraction of smooth, cardiac and skeletal muscle. Decarboxylation of histidine, a aminoacid, naturally found on fish, into biogenic amines, such as histamine, occurs at temperatures greater than 15°C. Histamine, an organic compound, derived from histidine is released from certain cells upon tissue injury or during the activity of certain antibodies. At high concentrations, they are risk factors for food intoxication whereas moderate levels may lead to food intolerance. Histamine is not inactivated by heat, therefore, proper cooking is not a remedy for improper storage. Patients sometimes describe a peppery or bitter taste to the fish, but often the fish tastes completely normal. A host of symptoms, including skin flushing, facial swelling, dizziness, throbbing headache, oral burning, metallic, sharp or peppery taste in mouth, abdominal cramps, nausea, vomiting, diarrhoea, palpitations, a sense of unease, and, rarely, prostration or loss of vision characterize scombroid poisoning. A rash that looks like sunburn may occur and a small number of patients have hives, i.e., allergic skin reaction. Symptoms usually occur within 10-30 minutes of ingesting fish and generally are self-limited.
Physical signs may include a diffuse erythema (a reddening of the skin due to capillary dilation), tachycardia, wheezing and hypotension or hypertension. Scombroid is second in incidence only 'to ciguatera poisoning, however, it often is misdiagnosed because it resembles an allergic reaction. Best precaution, therefore, is to avoid organ meats and gonads.